In general, the manufacture of semiconductor devices involves a so-called burn-in test, which is an accelerated test in which thermal and voltage loads are applied. If a characteristic value of a certain semiconductor device fails to meet predetermined standards as a result of the burn-in test, that semiconductor device is regarded as initially defective and excluded from the group of non-defective items.
In a vertical cavity surface emitting laser device, light is emitted perpendicularly to a semiconductor substrate. Therefore, a plurality of vertical cavity surface emitting laser devices may be subjected to the burn-in test while being arranged in an array on a wafer. Such a burn-in test is called a wafer level burn-in (WLBI).
There is a demand for technologies that realize accurate and low-cost WLBI for vertical cavity surface emitting laser arrays. For example, in a surface-emitting-type wafer disclosed in Japanese Unexamined Patent Application Publication No. 2006-66845), a plurality of surface-emitting-type elements are connected in series such that forward directions of light emitting element portions are the same.